Anti-Clotting Drug Based on Bat Saliva

Tuesday, September 28th 2004, 10:53 am

By: News On 6

LOUISVILLE, Ky. (AP) _ Stroke victims being treated at a Louisville hospital may benefit from the lessons of the vampire bat.

Researchers at University of Louisville Hospital are studying whether the bats' ability to drink the blood of an animal while preventing the blood from clotting might help control damaging strokes.

An experimental clot-busting drug modeled after bat saliva is being tested at University and 16 other sites.

One of the two study participants, 86-year-old Louis Wright of Beuchel, was introduced during a discussion of the research at the hospital Monday. Wright has improved markedly since his stroke in May.

``There was no hesitation'' about getting involved with the study, said his wife, Ann. ``We might help somebody else.''

Louis Wright had an ischemic stroke, which results when a clot or series of clots blocks blood supply to the brain. The longer the supply is denied, the greater the potential damage to the brain.

The only drug approved for the treatment of ischemic stroke, ``IV t-PA,'' must be administered within three hours of the onset of symptoms, said Dr. Kerri Remmel, director of the stroke service at University Hospital. Because many stroke victims arrive at a hospital too late, the drug is given to only a small percentage of patients.

The bat-saliva drug, known as desmoteplase, can be given up to nine hours after the onset of symptoms, can be administered quickly and is very potent, doctors said. Researchers believe that it works by breaking up clots and improving blood flow so that areas of the brain starving for blood don't die.

The idea came from nature. Vampire bats in the tropical regions of South America and Central America must take in up to 50 grams of blood daily, according to the drug's German manufacturer, Paion. To get that blood, they bite animals such as cows and donkeys.

Normally, an animal's blood would clot and close the wound. But since a bat's ``blood meal'' can take up to 30 minutes, it must stop the clotting. It accomplishes that with a protein in its saliva.

``Vampire bats can sit on the back of a cow's ear and suck blood all day long,'' Remmel said.

Paion, which has a logo resembling a bat in flight, isolated the protein and made a synthetic version, said Ronald S. Smith, research manager in the department of neurology at U of L.

The American Heart Association included the substance in its top 10 advances for 2003.

U of L got involved in the clinical trial in 2002, Smith said, and began enrolling patients last year. Wright was enrolled after being rushed to the hospital unable to speak or to move his right arm. Remmel said there is an 80 percent chance he got desmoteplase and a 20 percent chance he got a placebo.

If Wright did get the drug, it might have helped. At first, scans of Wright's brain showed a large area at risk of dying, but the region did not, doctors said.

Wright continued to improve with therapy and rehabilitation, doctors and therapists said, and he can speak in complex sentences, although he has trouble telling stories.

Research on the experimental drug is expected to continue for a couple of years, Smith said. Desmoteplase would have to be approved by the U.S. Food and Drug Administration before becoming available to the public.

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